The present invention relates to a data access method to a storage apparatus system in an information processing system or the like. More particularly, it relates to a data migration method within the storage apparatus system.
An increasingly prevailing trend is that a plurality of platforms and a plurality of storage apparatuses are connected to each other so that the platforms and the storage apparatuses will be integrated into so-called a single network. Here, the platforms are, for example, a personal computer, a workstation, and a mainframe which employ mutually different architectures and operating systems. This resultant network is generally referred to as “SAN (Storage Area Network)”, which is a technical term corresponding to “LAN (Local Area Network)” formed by connecting a plurality of computers by a network such as Ethernet. In SAN, usually, the computers and the storage apparatuses are connected using a communication line referred to as “Fibre Channel” formed of an optical cable or a copper wire.
It has been pointed out that SAN has several advantages. The first advantage is to provide an environment where the storage apparatuses can be accessed from the plurality of computers in common. The second advantage is that the data transfers among the storage apparatuses are made possible by interconnecting the storage apparatuses among themselves. This makes it possible to implement backups or data copies among the storage apparatuses without imposing a load onto the host computers, thereby, at the time of the storage apparatuses' failure, allowing the switching to storage apparatuses included in a secondary system. Thirdly, until now, the individual storage apparatuses have been connected to the individual computers, respectively. As a result, managing the individual storage apparatuses (i.e., monitoring the states of the apparatuses, and modifying the settings thereof) has been possible only from the individual computers connected thereto. In SAN, however, it becomes possible to manage all the storage apparatuses from an arbitrarily specified computer. Also, the conventional SCSI (Small Computer System Interface) could connect only 16 appliances at the maximum. Meanwhile, Fibre Channel can connect 100 or more appliances on-line, thereby making it possible to obtain an easy scalability.
In recent years, a large number of products for implementing SAN have appeared. There exists, however, none of the products that actually make full utilization of the above-described advantages. In the scalability in particular, although the on-line connection of the appliances has been made physically possible, fundamental technologies for taking full advantage of the scalability are lacking. In SAN, for example, when additionally installing a new disk apparatus for the replacement of an existing disk apparatus, the additional installation of the appliance can be carried out on-line. Concerning the data migration, however, the users usually need to explicitly instruct the data migration into the new disk apparatus after switching the connection off-line once. For the users to enjoy the merits by the appliance additional-installation during the on-line, in addition to the mere hardware additional-installation, it is also required to carry out the data migration or the like transparently to the users, i.e., in such a manner that the users are unconscious of the data migration or the like, in accompaniment with the hardware additional-installation.
Concerning the on-line data migration among the disk apparatuses, U.S. Pat. No. 5,680,640 has disclosed its example. The example in U.S. Pat. No. 5,680,640, which describes the data migration where the disk apparatuses designed for a mainframe are assumed, utilizes communication lines for connecting the disk apparatuses, and only disconnects the connections among the hosts and the disk apparatuses for a short time. After that, the example allows the data migration among the disk apparatuses to be implemented transparently to the users.
U.S. Pat. No. 5,680,640 allows the data migration among the disk apparatuses to be implemented unlimitedly transparently to the users. However, this is the data migration method where the for-mainframe-designed disk apparatuses are assumed, and thus this method is inapplicable to SAN. In the for-mainframe-designed disk apparatuses as disclosed in U.S. Pat. No. 5,680,640, when replacing an old disk apparatus by a new disk apparatus, the setting on the disk apparatus side makes it possible to make the new disk apparatus look as if it were the old disk apparatus when seen from the host side. This is made possible by manipulating the setting of device numbers or the like of the disk apparatuses.
However, in SAN, especially in the case of, e.g., the Fibre Channel environment, the individual unique IDs assigned to the individual disk apparatuses are determined by the negotiation among the appliances (i.e., the disk apparatuses, and a fibre channel switch) included in the network. Accordingly, the setting made by the users never changes the IDs. This condition, when using the data migration method in U.S. Pat. No. 5,680,640, makes it impossible to make the new disk apparatus disguise the old disk apparatus with respect to the host computers. Consequently, in reality, it is impossible to implement the data migration that is transparent to the hosts and the users.